Mixer-containers are known which enable mixing biopharmaceutical fluid. Such mixer-containers comprise an rigid outer containment device forming a housing for receiving a sterile disposable container. The container comprises a flexible wall defining an inner space to be filled with the biopharmaceutical fluid. The container also comprises a mixing member attached to a descending shaft. The shaft is attached to the container at a first bearing and a second bearing. The shaft of the container comprises, at the first bearing, a disc having magnets that can be placed facing a similar disc connected to a motor, the effect of the motor thus magnetically driving the shaft to rotate. The shaft can thus turn in order to mix the biopharmaceutical fluid.
Such a magnetic driving system requires precise alignment and positioning of the magnetic disc of the shaft and the magnetic disc of the motor to ensure optimal driving.
However, problems with geometric tolerances, due to the dimensional variability inherent in the manufacture of the component elements of the mixer-container, can lead to improper positioning of the magnetic discs of the shaft and of the motor facing one another when the container is installed into the rigid outer containment device. Furthermore, when mixing and heating the biopharmaceutical fluid, for example from temperatures of about 30-40 degrees Celsius, dilation of the plastic parts forming the mixer-container may occur. This changes the arrangement and position of the first bearing of the shaft relative to the motor, leading to improper operation of the mixer-container. It is then necessary to be able to adjust the positioning of the first bearing relative to the motor.
It is thus known to use a motor whose position is adjustable in height. However, the adjustment of such a motor can be difficult. If the motor is positioned too low, the arrangement of the first bearing and motor exerts stress on the shaft, which may result in bending or even breaking the shaft. In addition, an axial runout clearance of about 2 millimeters is required between the first bearing and the motor of the magnetic disc to allow the mixer-container to operate satisfactorily. A motor attached too low does not permit this clearance to exist, generating abrasion at the first bearing during operation of the mixer-container.
Conversely, if the motor is positioned too high, the container wall is subjected to tensile stress so that the motor and the first bearing can be positioned by each other. These stresses can damage the container wall, or even cause a tear resulting in a loss of biopharmaceutical fluid.
Adjustment and positioning of the motor can therefore be long and complicated in order to obtain satisfactory installation of the container in the rigid containment device.
Also known are containers comprising variable-length shafts, which enable folding the container by shortening the length of the shaft and facilitate container storage.
For example, patent WO 2015/039034 discloses bioreactor support structures comprising a telescopic shaft that can be used with containers of various sizes and shapes.
Patent U.S. Pat. No. 8,951,785 discloses a stirrer for a bioreactor, having a plurality of hingedly interconnected arms pivotable about a transverse axis of rotation. The shaft can thus have an adjustable height by folding the hinged arms.
WO 2009/143925 discloses a container having two adjacent shaft members each having a hollow body into which one of the two shaft members can slide. An elastic member is located between the hollow body and the filling body in order to allow transmission of rotational movement between the two members. An opening is provided in the wall of the hollow body, to balance the pressure in the hollow body and in the rest of the container. A hydrophobic gas-permeable membrane is placed across the opening to prevent fluid entering the hollow body from the container.
However, such a shaft is difficult to implement since it is necessary to provide a hydrophobic membrane over the opening of the hollow body. Furthermore, in the case of a circular shaft, the elastic member only allows transmitting low torques, preventing efficient mixing of the fluid filling the container.